There have been previous attempts in the art to increase the tamper resistance of dosage forms, such as opioid analgesic dosage forms. Prior approaches to developing tamper resistant opioid dosage forms have included combining an opioid agonist with an opioid antagonist. Particular examples of such combinations include compositions including naloxone and morphine or oxymorphone (U.S. Pat. No. 3,493,657 to Lewenstein et al.); methadone and naloxone (U.S. Pat. No. 3,773,955 to Pachter et al.); methadol or acetyl methadol and naloxone (U.S. Pat. No. 3,966,940 to Pachter et al.); oxycodone and naloxone (U.S. Pat. No. 4,457,933 to Gordon et al.); and buprenorphine and naloxone (U.S. Pat. No. 4,582,835 to Lewis et al.).
U.S. Pat. No. 6,228,863 to Palermo et al. discloses an oral dosage form which combines an opioid agonist and an opioid antagonist such that at least two separation steps are required to isolate the agonist.
U.S. Pat. No. 5,935,975 to Rose et al. discloses methods for treating drug dependency by the combined administration of the drug, i.e. the agonist, and an antagonist of the drug.
U.S. Patent Application Publication No. 2003/0143269 A1 to Oshlack et al. discloses a dosage form comprising an opioid against in releasable form and a sequestered opioid antagonist which is not substantially released following administration of the intact dosage form.
In addition, it is known in the pharmaceutical art to prepare oral dosage forms which provide for controlled release of therapeutically active agents. Such controlled release compositions are used to delay absorption of at least a portion of the dose of the agent until it has reached certain portions of the gastrointestinal tract. Such controlled release of the agent serves to maintain a desired concentration of the agent in the blood stream for a longer duration than would occur if conventional immediate or rapid release dosage forms were to be administered.
Over the years, several different methods of preparing controlled release pharmaceutical dosage forms have been suggested, including, for example, extrusion, granulation, coating beads and the like.
There remains a need in the art for improved tamper resistant dosage forms and improved techniques for their preparation.